The background description provided herein is for the purpose of generally presenting the context of the present disclosure. The subject matter discussed in the background of the invention section should not be assumed to be prior art merely as a result of its mention in the background of the invention section. Similarly, a problem mentioned in the background of the invention section or associated with the subject matter of the background of the invention section should not be assumed to have been previously recognized in the prior art. The subject matter in the background of the invention section merely represents different approaches, which in and of themselves may also be inventions. Work of the presently named inventors, to the extent it is described in the background of the invention section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A light emitting device (LED), sometimes also referred to as a light emitting diode, is a sort of semiconductor device that changes electricity into infrared rays or light by using the characteristics of compound semiconductors to input/output a signal, which may be used as a light source. Typically, a LED package includes a package body, also referred to as a lead frame package, and one LED chip (or multiple LED chips) electrically connected to terminals of the package body via small metal wires such as gold wires. For example, in a semiconductor device using a conventional lead frame package, the a conventional package body may have a lead frame substrate that is typically coated with a metal such as silver, which functions as a lead frame, and a thermoplastic body that is made of thermoplastic resin and formed on and around the lead frame substrate. The thermoplastic body may form a reflecting cup, which has a bottom reflecting surface on the surface of the lead frame substrate. However, the thermoplastic resin of the thermoplastic body has little adhesion with the lead frame substrate, and the resin part of the thermoplastic body and the lead frame substrate are likely to be detached. Further, the interface between the reflecting cup of the thermoplastic body and the bottom reflecting surface on the lead frame substrate shows potential for gas leakage due to the low adhesion between these two materials, as disclosed in U.S. Pat. No. 8,530,250. Moreover, the metal coating of the lead frame is very expensive and time consuming. The metal coating also causes long-term reliability issues such as sulfidation on silver plating which reduces the optical output. Conventional LED package also has an encapsulating layer that covers the LED chip (or LED chips) and fills the cavity of the lead frame or the chip-on-board package. The encapsulating layer usually has low thermal dissipation property that restricts heat flow.
Generally, LED package design involves the simultaneous integration and balancing of many different design factors including optical, thermal, mechanical, and electrical challenges. Designing of LED package becomes more challenging to ensure the reliability of an LED package as the demand of power per package area increases. High power density per unit area could lead to material failures including delamination of integrated parts of LED package and degradation of reflectivity and optical properties of materials.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.